The present invention relates to devices and methods for applying tape to surfaces.
One known method for forming a lens of glass or polymeric material for use in a pair of eye glasses is to first form a first major surface on a lens blank for the lens. The first major surface can be made planar but most often is made generally convex, and when it is formed on a polymeric lens blank can have discontinuities when the lens is to be of the "bifocal" or "trifocal" type including portions having different focal lengths. A piece of special pressure-sensitive adhesive-coated tape is then adhered over the finished first major surface (i.e., such as the tape described in U.S. patent application Ser. No. 36,878, filed concurrently herewith, the content whereof is incorporated herein by reference), and a block is centrally affixed to the outer surface of the tape via a low melting temperature metal composition. The block is then engaged in machines that form a properly shaped second major surface (which is normally concave) on the side of the lens blank opposite the tape, after which the block is removed and the tape is peeled away from the finished lens.
To produce an accurate lens by this method it is important that the tape be smoothly applied to the lens blank to ensure firm attachment of the block by the metal composition, and (particularly to produce an accurate polymeric lens) that no air be trapped between the tape and the lens blank so that the block via the metal composition can give complete support to the first major surface formed on the lens blank. If air is present so that such support is not provided, the operation for forming the second major surface on a polymeric lens blank can distort the lens blank, which distortion results in imperfections in the lens.
Prior to the present invention the only known methods of applying the tape were either manually tensioning the tape across while pressing the tape against the first major surface for the lens blank, which method is difficult and tedious to perform and produces results which vary greatly depending upon applier's patience and skill; or pressing the tape against the first major surface for the lens via a soft comformable resilient elastic member that conforms to the major surface to press the tape into position.